The libxl_domain_config_from_json API appeared in Xen 4.5, hence
there is no need to check for its existence after changing the
minimum supported Xen version to 4.6. Remove the check and its
use in the tests.
Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>